Effects of elevated temperature on basalt and glass FRP bars in prismatic beams under flexural loading

Abstract

Fiber-reinforced polymer (FRP) reinforcement has gained significant attention in research and structural applications due to its desirable mechanical properties and durability. Advances have been made in understanding FRP’s resistance to elevated temperatures; however, uncertainties persist due to inconsistencies in the available experimental data. This study presents an experimental investigation into the effects of various parameters on the performance of reinforced concrete (RC) prismatic beams exposed to elevated temperatures. Key parameters included reinforcement type (steel, Glass FRP (GFRP), and Basalt FRP (BFRP), bar diameter (16 mm and 20 mm), surface texture (ribbed and sand-coated), and concrete cover (40 mm and 60 mm). The prismatic beams were subjected to target temperatures of 200, 400, and 700 °C, followed by testing in a four-point loading setup. The experimental results revealed that BFRP-reinforced prismatic beams exhibited a 17 % higher residual load-carrying capacity and 32.3 % greater toughness at 200 °C and 400 °C, but a 22 % lower capacity and 26.9 % reduction in toughness at 700 °C compared to their GFRP-reinforced counterparts. Additionally, prismatic beams reinforced with sand-coated GFRP bars showed up to a 27 % improvement in load-carrying capacity compared to those with ribbed GFRP bars, and a larger concrete cover contributed to better overall flexural performance of the prismatic beams under elevated temperatures.